[xubuntu] Intel Centrino Advanced-N 6205 not working on XUbuntu 11.4

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Hey,
I just can't connect to a wirless Network using the build in networkdevice. The Networkmanger shows "device not manged". It has been connected to the network during the setup prozess.
Another usb Wirlesscard is working perfect (curently pluged in under wlan1) but I want to use the buildin.
Here are some Information's. If you need more just ask.
1 ) Machine Brand and Model (PC/Laptop):
Laptop Thinkpad x220
2 ) Wireless Brand, Model and Wireless Chipset:
Code:
$ lspci -nn | grep -i Net
03:00.0 Network controller [0280]: Intel Corporation Centrino Advanced-N 6205
(Hardware)